Guillermina Yáñez

Relationship of specific EEG frequencies at specific brain areas with performance.

THIS study shows that incorrect responses are preceded by different EEG characteristics than correct responses, and that these differences appear in specific brain regions that participate in each particular task. EEGs were recorded in children during three different tasks: color discrimination (CDT), verbal working memory (VWM), and word categorization task (WCT). EEG segments previous to the presentation of the stimulus were analysed. Incorrect responses were preceded by lower EEG power values at 7.8 Hz in posterior temporal and right parietal leads in CDT, 8.59 and 9.36Hz in frontal areas in VWM, and 10.72 Hz in the left hemisphere in WCT. In the former task > 1.56 Hz power in frontal areas prior to an incorrect response was also observed.

Auditory event-related potentials in poor readers

Although poor readers (PR) are considered the major group among reading-disabled children, there are not event-related potentials (ERP) studies reported of PR on the subject. In this study, attentional and memory processes were studied in an auditory oddball task in PR and normal controls. ERP to auditory stimuli were recorded in 19 leads of the 10/20 system, using linked earlobes as references, in 20 normal children (10 female) and 20 PR (10 female) of the same age (10-12 years old). Two pure tones (1000 and 3000 Hz) were used in an oddball paradigm. No significant differences were observed in the amplitudes and latencies of N100 between the groups. However, N200 to frequent stimuli and P200 to both frequent and infrequent stimuli were of higher amplitude in poor readers than in normal children. There were no differences between groups in the latency and amplitude of P300. The results suggest that PR use more attentional resources in the components occurring before P300 to both frequent and infrequent stimuli than the normal children, and this finding is particularly marked for PR girls.

Narrow-band spectral measurements of eeg during emotional tasks

Broad band spectral measurements were calculated on EEG recordings of 40 healthy male university students during emotional tasks using the emotion induction technique. Emotional stimuli were sentences with positive valence (joy of love), with negative valence (frustration) and neutral situation. Broad band measurements showed that delta and beta bands reflected better the differences by emotional state. Hemispheric differences associated to emotional states were obtained only for mean frequency data. Highe delta frequencies at left frontopolar, right frontal, parietal and temporal and higher beta frequencies at left frontotemporal and temporal were related to love. Meanwhile higher delta frequencies especially at left frontopolar and temporal regions and lower beta frequencies at midline frontal (Fz) and central (Cz) leads were associated to frustration. These findings suggest that narrow band measurements may reflect more efficiently EEG changes during emotional tasks.

A follow-up study of EEG coherences in children with different pedagogical evaluations

A follow-up study on EEG coherence values was carried out with 46 school-age children divided into three pedagogical groups considering their reading and writing abilities (normal subject and children with mild and with serious reading-writing problems). EEGs were recorded at rest, with eyes closed in 15 referential derivations that gave 105 possible coherence values. Coherence was calculated after the elimination of the average reference. Repeated Measure ANOVAs were calculated to evaluate the effects of time, sex, reading-writing problems and their interactions. The second EEG recordings were taken 2-3 years after the first. The results revealed significant increase of coherence values during the time lapse studied, consisting of an increase of frontal coherences in all bands, with the exception of the theta band. The most numerous changes occurred in the alpha band. Very few differences in coherence values were observed between the two EEG recordings by pedagogical groups and by sex suggesting a similar but not igual maturation of coherences of boys and girls and of the three pedagogical groups, in this age range studied. These findings suggests an abnormal coherence development for the reading disabled group, as well as different coherence maturation for boys and girls in this time lapse studied.

Poor reading skills may involve a failure to focus attention

A source localization analysis was carried out to provide brain functional and structural assessments of individuals with poor reading skills. Standardized low-resolution brain electromagnetic tomography was used to locate sources of P2 and P3 event-related potential components in normal readers and in poor reader children performing a cued continuous performance task. Cue-elicited P2 sources in the right superior parietal gyrus were smaller in 37 poor readers than in 40 normal readers. Poor readers showed a higher P3 activation in response to a false target in frontal and frontorbital regions than normal readers. These results suggest that reading disabilities may be attributed to failures in attentional focalization for incoming stimuli.

Adaptación de las pruebas de procesamiento fonológico de una batería neuropsicológica en niños de 5 a 7 años

Resumen Se ha descrito la importancia de las habilidades de procesamiento fonológico y en especial el de la sensibilidad fonológica, en la adquisición de la lectura, por lo) que es muy importante evaluar estas habilidades en niños preescolares. El objetivo del presente trabajo fue realizar una adaptación de las pruebas de procesamiento fonológico de la Batería Neuropsicológica para la Evaluación de Niños con trastornos del Aprendizaje de la Lectura (BNTAL) para niños mexicanos preescolares y de primer grado escolar. Participaron 165 niños de 5.5 a 7.4 años, de preescolar y primer grado. Los resultados mostraron un nivel de consistencia interna bastante aceptable para las pruebas de sensibilidad fonológica, además se observaron significativamente mejores ejecuciones en los niños de primer grado escolar con relación a los preescolares en la mayoría de las pruebas de sensibilidad fonológica. Se concluye que el instrumento de medición obtenido es confiable para medir el procesamiento fonológico de los niños de estas edades.

Procesamiento fonológico y léxico en niños normolectores de Educación Primaria

Resumen Las habilidades fonológica y léxica son esenciales para el reconocimiento de palabras escritas, pero el grado de su participación cambia con el desarrollo de la lectura. Aún no se ha establecido un punto específico en el desarrollo que represente la transición de la dependencia de las habilidades fonológicas a las de reconocimiento léxico directo. En este trabajo se estudia la participación de factores fonológicos y léxicos en el procesamiento de palabras escritas, en niños con diferentes niveles de automatización de la lectura, mediante la ejecución en una tarea de decisión fonológica con interferencia léxica y una de decisión léxica con interferencia fonológica. Participaron 164 niños (7–13 años), de 2°, 4° y 6° de educación básica de la Ciudad de México. Se observó interferencia léxica y fonológica en los niños de 2°, en los de 4° la interferencia fonológica fue menor mientras que en el 6° no hubo ninguna interferencia. Los hallazgos sugieren falta de automatización en el reconocimiento de palabras escritas en los niños de 2°, la automatización parece establecerse en 4°.

Adolescents with vascular frontal lesion: A neuropsychological follow up case study

The objective of this research was to identify clinically significant changes in cognitive functions in three adolescents who underwent surgery for resection of a focal vascular lesion in the frontal lobe. Cognitive functions, executive function, behavior regulation, emotion regulation, and social abilities were assessed prior to surgery, six and 24 months post-discharge. Significant clinical changes were observed during all the assessments. Cognitive changes after surgery are not homogeneous. Most of the significant clinical changes were improvements. Especially the significant clinical changes presented in EF domains were only improvements; these results suggest that EF were affected by the vascular lesion and benefitted by the surgery. After resection of a vascular lesion between 15 and 16 years of age the affected executive functions can continue the maturation process. Our results highlight the importance that assessments must include emotional aspects, even if deficits in these domains are not presented in the acute phase. Rehabilitation methods should promote the development of skills that help patients and their families to manage the emotional and behavioral changes that emerge once they are discharged from the hospital.

Quantitative spectral EEG assessments during affective states evoked by the presentation of the international affective pictures

Resumen en: This study was carried out to find changes in EEG power during emotions of positive and negative valence evoked by the International Affective Pictures. ...